Heat exchanger

ABSTRACT

A heat exchanger includes a core portion and at least one substantially straight header plate. The core portion includes a plurality of heat exchanger tubes and fins disposed alternatively. The at least one substantially straight header plate has a plurality of insertion slots extending therethrough for receiving a respective end of the heat exchanger tubes therein, the core portion and the at least one header plate being brazeable together

FIELD OF THE INVENTION

The invention relates to heat exchangers and, more particularly, to amethod for manufacturing heat exchangers such as radiators, oil coolers,air-to-air heat exchangers (charge air coolers “CAC”), compressors, fuelcoolers, conditioned air units, and the like.

DESCRIPTION OF THE PRIOR ART

Radiators are heat exchangers that are used to reject heat from thecoolant of an internal combustion engine to the ambient. The enginecoolant is typically circulated through coolant passages in the engineblock to the so-called liquid side of the radiator where it is cooledand then returned to the engine block. Cooling occurs by forcing ambientair through the radiator core.

The thermal efficiency of an engine typically increases as its operatingtemperature is increased. Consequently, it is desirable to raise theoperating temperature of the engine as much as possible to maximizeefficiency. The operating temperature can hardly be raised to the pointwhere the coolant within cooling passages in the engine begins tovaporize.

Consequently, if engines are to be operated at higher temperatures, itis necessary that the boiling point of the coolant being employed beraised. This can be done by increasing system pressure. At the sametime, it becomes necessary to increase the strength of the radiator Iheat exchanger so that the same can operate at the increased pressure.

Oil coolers are heat exchangers wherein heat dissipation occurs throughoil. Oil viscosity increases in cold temperature. Thus, when operatingin relatively cold conditions or when the motor associated with the oilcooler is cold, the oil cooler must sustain high pressure.

Finally, radiators and charge air coolers have a longer operating lifeif they can support higher pressure when operating in high vibratingenvironment.

BRIEF SUMMARY OF THE INVENTION

It is therefore an aim of the present invention to address the abovementioned issues.

According to a general aspect, there is provided a heat exchangercomprising: a core portion including a plurality of heat exchanger tubesand fins disposed alternatively; and at least one substantially straightheader plate having a plurality of insertion slots extendingtherethrough for receiving a respective end of the heat exchanger tubestherein, the core portion and the at least one header plate beingbrazeable together.

According to another general aspect, there is provided a heat exchangercomprising: a core portion including a plurality of heat exchangertubes; at least one substantially straight header plate having aplurality of insertion slots defined therein for receiving a respectiveend of the heat exchanger tubes therein, the core portion and the atleast one header plate being brazeable together; and at least one tankcover securable to the at least one header plate and defining a tankcavity with the at least one header plate when secured thereto, the heatexchanger tubes being in fluid communication with the tank cavity.

According to still another general aspect, there is provided a methodfor manufacturing a heat exchanger comprising: inserting a respectiveend of a plurality of heat exchanger tubes in a respective insertionslot extending through a substantially straight header plate to define aheat exchanger tube and header plate assembly; and brazing the heatexchanger tube and header plate assembly.

According to a further general aspect, there is provided a heatexchanger header comprising: a brazeable substantially straight headerplate having an inner surface, an outer surface opposed to the innersurface, a plurality of tube insertion slots extending throughout theheader plate and extending in a longitudinal succession; and a tankcover having peripheral edges secured to the outer surface of the headerplate, proximate to external edges of the header plate, and defining atank cavity with the header plate, the tube insertion slots being influid communication with the tank cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat exchanger in accordance with anembodiment;

FIG. 2 is a sectional view taken along cross-section lines 2-2 of FIG. 1of the heat exchanger;

FIG. 3 is a perspective view of a core portion and two header plates ofthe heat exchanger shown in FIG. 1;

FIG. 4 includes FIG. 4 a and FIG. 4 b, FIG. 4 a is a top plan view ofthe core portion and one of the header plates shown in FIG. 3 and FIG. 4b is an enlarged view, fragmented, of heat exchanger tubes inserted incavities defined in one of the header plates;

FIG. 5 is a perspective view, partly sectioned and fragmented, of theheat exchanger shown in FIG. 1; and

FIG. 6 is a flow chart illustrating a method for manufacturing the heatexchanger shown in FIG. 1.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

FIGS. 1 and 2 show a heat exchanger 10 having a housing 12 covering acore portion 14 and extending between a pair of hollow headers 16disposed in parallel with each other. Fluid inlet and outlet connectors18 are mounted to the headers 16 and are in fluid communication with atank cavity 20 defined in the hollow headers 16, as will be described inmore details below.

The housing 12 includes two opposed and spaced-apart side plates 24having an edge secured to headers 16.

FIGS. 2 and 3 show an internal view of the heat exchanger 10. The coreportion 14 includes a plurality of heat exchanger flat tubes 26 disposedin parallel with their opposite sides in fluid communication with thehollow headers 16. Corrugated fins 28 are disposed between adjacent heatexchanger tubes 26 and outside the outermost heat exchanger tubes 26.The side plates 24, defining a portion of the housing 12, are disposedoutside the outermost corrugated fins 28.

The heat exchanger tubes 26 are hollow extruded articles defining aninner channel 30 with an obround cross-section. The inner channel 30 isin fluid communication with the tank cavities 20. The inner channel 30can be divided into a plurality of passages with partition walls (notshown), also called micro-channel tubes, extending longitudinallytherein to reinforce the tubes 26.

Each header 16 includes a substantially straight rectangular headerplate 32 having an inner surface 34 and an opposed outer surface 36. Thesubstantially straight header plates 32 do not include upwardlyextending peripheral edges like in prior art heat exchangers. The innersurfaces 34 of both headers 16 face one another when the heat exchanger10 is assembled. A plurality of tube insertion slots 38 extendthroughout the header plates 32 in a longitudinal succession as shown inFIG. 4 a. The insertion slots 38 are defined to receive therein an endof one heat exchanger tube 26. FIG. 4 b shows that the outer surface ofthe heat exchanger tubes 26, proximate to an end thereof, is juxtaposedto the inner surface of the insertion slots 38. Thus, the external sizeof the heat exchanger tubes 26 is slightly smaller than the size of theinsertion slots 38. In an embodiment, the insertion slots 38 in headerplate 32 are created by machining.

FIGS. 2 and 5 show that each header 16 also includes a tank cover 40having an upper wall 42, two opposed and spaced-apart lateral walls 44,and two opposed and spaced-apart side walls 46, extending between thelateral walls 44. The lateral walls 44 and the side walls 46 haveperipheral edges 48 secured to the outer surface 36 of the header plate32, proximate to external edges 50 of the header plate 32. For exampleand without being limitative, the peripheral edges 48 of the tank cover40 can be welded to the header plate 32. In the embodiment shown, theside walls 46 are recessed internally from the external edges 50 of theheader plate 32. The tank cover 40 and the header plate 32 define thetank cavity 20 when secured together.

In an alternative embodiment (not shown), the peripheral edges 48 of thetank cover 40 can be welded to the lateral walls of the heater plate 32,i.e. the walls extending between the inner surface 34 and the outersurface 36. In another alternative embodiment (not shown), the outersurface 36 of the heater plate 32 can include a peripheral recesssection in which the peripheral edges 48 of the tank cover 40 areinserted and secured. The peripheral recess section can be machined inthe header plate 32. In another alternative embodiment (not shown), boththe edges of the header plate 32 and the peripheral edges 48 of the tankcover 40 can be beveled edges which are matingly engaged when securingthe tank cover 40 to the header plate 32.

The tank cavity 20 is in fluid communication with the inner channels 30of the heat exchanger tubes 26 inserted in the tube insertion slots 38and with the fluid inlet and outlet connectors 18.

In the embodiment described above, the heat exchanger is a single tubepass heat exchanger wherein the fluid enters the heat exchanger at oneend, flows once in the tubes, and exits at the opposed heat exchangerend. In alternative embodiments, the heat exchanger can be a multipletube pass heat exchanger such as and without being limitative a doubletube pass or a triple tube pass heat exchanger. For example and withoutbeing limitative, in a double tube pass heat exchanger, the fluid entersthe heat exchanger at a first end, flows twice in the tubes, and exitsat the first end. Similarly, in a triple tube pass heat exchanger, thefluid enters the heat exchanger at a first end, flows thrice in thetubes, and exits at the opposed heat exchanger end. In multiple tubepass heat exchangers, at least one of the tank covers includes apartition wall which separated the tank cavity into separated chambers.It is appreciated that the heat exchanger can include more than threepasses.

Referring now to FIG. 6, for manufacturing a heat exchanger, the coreportion is first assembled to the header plates 70. The heat exchangertubes and the corrugated fins are stacked alternatively and the oppositeends of the heat exchanger tubes are inserted in the correspondinginsertion slots defined in the header plates to form a provisionalassembly, as shown in FIG. 3. The edges of the heat exchanger tubesextend substantially flush with the outer face of the header plate inwhich they are inserted. Furthermore, side plates are assembled to thecore portion. Then, this provisional assembly is integrally brazed in afurnace 72.

The brazing step is carried out in a controlled environment in anatmosphere of inert gas such as nitrogen, for instance, during 10 to 20minutes and, in an alternative embodiment, during 12 to 18 minutes. Thetemperature in the furnace ranges between approximately 1000 and 1200°F. (approximately 530 and 650° C.). It is appreciated that the brazingconditions (temperature, atmosphere, time, etc.) can vary in accordancewith the heat exchanger size and materials.

More particularly, in an embodiment, prior to the brazing step, abrazing flux is deposited on the provisional assembly throughelectromagnetism. The use of these fluxing agents with aluminum heatexchangers promotes the dissociation and disruption of the nativealuminum oxide (Al₂O₃). Then, the provisional assembly is introduced ina controlled environment where vacuum is created. Nitrogen is introducedand the temperature in the controlled environment is increased toapproximately 400-450° F. (approximately 200 and 230° C.) for apre-heating step. Following the pre-heating step, the provisionalassembly is brazed as mentioned above. The brazed assembly is thencooled in the controlled environment, under nitrogen, wherein thetemperature is lowered to approximately 400° F. Finally, the brazedassembly is removed from the controlled environment and cooled toambient temperature under forced air convection.

Then, the tank covers are mounted to a respective header plate andsecured thereto 74. In an embodiment, the peripheral edges of the tankcovers are secured to the outer face of the header plate, proximate toexternal edges of the header plate, to define the tank cavity. Theperipheral edges can be welded to the header plate for securing the tankcovers.

Finally, the side plates are sawed to create dilatation joints 54(FIG. 1) therein 76. It is appreciated that, in an alternativeembodiment, the dilatation joints can be sawed before securing the tankcover to the brazed assembly.

In an alternative embodiment, the provisional assembly can include tankcovers. The tank covers are thus secured by brazing simultaneously withthe other components. They can also be welded to the header plates priorto the brazing step.

The heat exchanger tubes, the corrugated fins, and the headers 16 aremade of an aluminum alloy adapted for heat exchanger applications. Forexample and without being limitative, they can be made of AA 3003. Theheat exchanger tubes, the corrugated fins, and the header plates includea surface clad. For example and without being limitative, the cladmaterial can be 4000 series aluminum. It is appreciated that, inalternative embodiments, other aluminum alloys adapted for heatexchanger and brazing applications can be used.

The header plates can either have a clad on both sides or on only oneside, either the inner surface or the outer surface. Similarly, thecorrugated fins can have a clad on both sides or on only one side. Theouter surface of the heat exchanger tubes includes the clad material.The clad material can represent between 2 and 15% of the heat exchangercomponent thickness. In an alternative embodiment, the clad material canrepresent between 5 and 10% of the heat exchanger component thickness.

In a non-limitative embodiment, the header plates are rectangular with alength ranging between 75 and 1020 millimeters (mm) (2.95 and 40.0inches), a width ranging between 12.7 and 180 mm (0.5 and 7.0 inches),and a thickness ranging between 2.0 and 12.7 mm (0.08 and 0.5 inch). Inan alternative embodiment, the header plates have a length rangingbetween 100 and 950 mm (4 and 37.5 inches), a width ranging between 19and 170 mm (0.75 and 6.75 inches), and a thickness ranging between 2.5and 10 mm (0.1 and 0.4 inch).

In an embodiment, the heat exchanger tubes have a cross section length(major diameter) ranging between 19 and 120 mm (0.75 and 4.8 inches) anda cross-section width (minor diameter) ranging between 2 and 12 mm (0.08and 0.5 inch). In an alternative embodiment, the heat exchanger tubeshave a cross section length ranging between 25 and 80 mm (1.0 and 3.15inches) and a cross-section width ranging between 3.7 and 7 mm (0.15 and0.28 inch).

In an embodiment, the thickness of the heat exchanger tube wall rangesbetween 0.1 and 3.6 mm (0.004 and 0.14 inch) and in an alternativeembodiment, the thickness of the heat exchanger wall ranges between 0.2and 3.2 mm (0.008 and 0.125 inch). In an embodiment, the thickness ofthe heat exchanger tube wall can vary along the tube length.

In an embodiment, the distance between the external edges of the headerplate and the outermost heat exchanger tubes ranges between 1.3 and 3.2mm (0.05 and 0.125 inch). In an alternative embodiment, this distanceranges between 1.3 and 6.4 mm (0.05 and 0.25 inch).

As mentioned above, the thickness of the header plates ranges between2.0 and 12.7 mm (0.08 and 0.50 inch). In comparison with the headers ofprior art heat exchangers, the header plate is thicker, providing anincreased stiffness to the resulting heat exchanger and a strongerphysical bond between the heat exchanger tubes and the header platesince brazing occurs on a larger surface area. The resulting headerplate and tube exchanger assembly can thus support higher pressure.

Moreover, the outermost heat exchanger tubes are mounted proximate tothe external edge of the header plate since the header plate issubstantially straight. Thus, the moment arm between the junction of theexchanger tubes and the header plate and the external edges of theheader plate is reduced. The resulting heat exchangers have improvedmechanical properties, such as higher pressure resistance, stiffness,vibration resistance, and impact strength, comparatively to prior artheat exchangers.

Comparatively, to prior art heat exchangers wherein the tank cover ismounted inwardly of the header plates having turn up edges, the heatexchanger has a higher burst pressure strength. For example, in anembodiment, the heat exchanger withstood 1825 psi comparatively to 580psi for the prior art heat exchanger. Moreover, the heat exchanger didnot show any cracking comparatively to the prior art heat exchangerwhich showed cracking at 300 psi.

It is appreciated that the heat exchangers described above can be usedin radiators, compressors, fuel coolers, conditioned air units,air-to-air heat exchangers (charge air coolers), oil coolers, and thelike.

It can be used in new products (OEM) or replacement products.

The embodiments of the invention described above are intended to beexemplary only. For example, the shape of the heat exchanger tubes canvary and the shape of the insertion slots can vary accordingly.Furthermore and without being limitative, the shape of the headers canvary. The position of fluid inlet and outlet connectors can be modifiedfrom the one described above in reference to FIG. 1, which is typicallyassociated with oil coolers. For example and without being limitative,for radiators and charge air coolers, the fluid inlet and outletconnectors can be centrally mounted to a respective hollow header.

The scope of the invention is therefore intended to be limited solely bythe scope of the appended claims.

1. A heat exchanger comprising: a core portion including a plurality ofheat exchanger tubes and fins disposed alternatively; and at least onesubstantially straight header plate having a plurality of insertionslots extending therethrough for receiving a respective end of the heatexchanger tubes therein, the core portion and the at least one headerplate being brazeable together.
 2. A heat exchanger as claimed in claim1, wherein the distance between external edges of the at least oneheader plate and the outermost heat exchanger tubes ranges between 1.3and 3.2 mm.
 3. A heat exchanger as claimed in claim 1, wherein the atleast one header plate has a thickness ranging between 2.0 and 12.7 mm.4. A heat exchanger as claimed in claim 1, comprising at least one tankcover weldable to the at least one header plate and defining a tankcavity with the at least one header plate when secured thereto, the heatexchanger tubes being in fluid communication with the tank cavity.
 5. Aheat exchanger as claimed in claim 4, wherein the at least one tankcover is welded to an outer surface of the at least one header plate,proximate to external edges thereof.
 6. A heat exchanger as claimed inclaim 4, wherein the at least one tank cover is welded to the brazedcore portion and the at least one header plate assembly.
 7. A heatexchanger as claimed in claim 1, wherein at least one of the heatexchanger tubes, the fins, and the at least one header plate includes aclad for brazing the core portion and the at least one header platetogether.
 8. A heat exchanger as claimed in claim 1, wherein the atleast one header plate comprises two header plates parallel to eachother and wherein the header plates are upwardly extending external edgefree.
 9. A heat exchanger as claimed in claim 8, wherein the headerplates are substantially rectangular and have a length ranging between75 mm and 1020 mm and a width ranging between 12.7 mm and 180 mm.
 10. Aheat exchanger comprising: a core portion including a plurality of heatexchanger tubes; at least one substantially straight header plate havinga plurality of insertion slots defined therein for receiving arespective end of the heat exchanger tubes therein, the core portion andthe at least one header plate being brazeable together; and at least onetank cover securable to the at least one header plate and defining atank cavity with the at least one header plate when secured thereto, theheat exchanger tubes being in fluid communication with the tank cavity.11. A heat exchanger as claimed in claim 10, wherein the distancebetween external edges of the at least one header plate and theoutermost heat exchanger tubes ranges between 1.3 and 3.2 mm.
 12. A heatexchanger as claimed in claim 10, wherein the at least one header platehas a thickness ranging between 2.0 and 12.7 mm.
 13. A heat exchanger asclaimed in claim 10, wherein the at least one tank cover is weldable toan outer surface of the at least one header plate, proximate to externaledges thereof.
 14. A heat exchanger as claimed in claim 10, wherein theat least one tank cover is welded to the brazed core portion and the atleast one header plate assembly.
 15. A heat exchanger as claimed inclaim 10, wherein at least one of the heat exchanger tubes and the atleast one header plate includes a clad for brazing the core portion andthe at least one header plate together.
 16. A heat exchanger as claimedin claim 10, wherein the at least one header plate comprises two headerplates parallel to each other and wherein the header plates are upwardlyextending external edge free,
 17. A heat exchanger as claimed in claim10, wherein the core portion comprises fins in alternating successionwith the heat exchanger tubes.
 18. A method for manufacturing a heatexchanger comprising: inserting a respective end of a plurality of heatexchanger tubes in a respective insertion slot extending through asubstantially straight header plate to define a heat exchanger tube andheader plate assembly; and brazing the heat exchanger tube and headerplate assembly.
 19. A method as claimed in claim 18, further comprisingsecuring a tank cover to the straight header plate for defining a tankcavity, the heat exchanger tubes being in fluid communication with thetank cavity.
 20. A method as claimed in claim 19, further comprisingwelding the tank cover to an outer surface of the header plate,proximate to external edges thereof.
 21. A method as claimed in claim19, wherein the securing step is carried out after the brazing step. 22.A method as claimed in claim 18, further comprising disposing corrugatedfins between consecutive heat exchanger tubes and wherein the brazingstep is carried out on the heat exchanger tube and straight header plateassembly including the corrugated fins.
 23. A method as claimed in claim18, further comprising creating the insertion slots in the header platewherein the distance between external edges of the header plate and theoutermost insertion slots ranges between 1.3 and 3.2 mm.
 24. A heatexchanger header comprising: a brazeable substantially straight headerplate having an inner surface, an outer surface opposed to the innersurface, a plurality of tube insertion slots extending throughout theheader plate and extending in a longitudinal succession; and a tankcover having peripheral edges secured to the outer surface of the headerplate, proximate to external edges of the header plate, and defining atank cavity with the header plate, the tube insertion slots being influid communication with the tank cavity.
 25. A heat exchanger header asclaimed in claim 24, wherein the distance between the external edges ofthe header plate and the outermost insertion slots ranges between 1.3and 3.2 mm.
 26. A heat exchanger header as claimed in claim 24, whereinthe header plate has a thickness ranging between 2.0 and 12.7 mm.
 27. Aheat exchanger header as claimed in claim 24, wherein the tank cover iswelded to the header plate after the header plate has been brazed.
 28. Aheat exchanger header as claimed in claim 24, wherein the header plateincludes a clad to braze the header plate with a core portion.
 29. Aheat exchanger header as claimed in claim 24, wherein the header plateis substantially rectangular and has a length ranging between 75 mm and1020 mm and a width ranging between 12.7 mm and 180 mm.